Treatment of 4-(1,2-dimethylindoI-3-yI) butyric acid (1 ) with trifluoroacetic anhydride gives either 1methyl-2-trifluoroacetylmethyleneindoline-3-spirocyclopentan -2'-one (6) or lr2-dimethyl-6-oxo-3,4,5,6tetrahydro-1 H-cyclohept [c,d]indole (5) depending on the reaction conditions. 3-(1,2-Dimethylindol-3-y1)propionic acid (1 0; R = OH) reacts with trifluoroacetic anhydride to form 4,4a-dihydro-9-methyl-4a-[ 2,2,2-trif luoro-1 -(2hydroxy-9met hylcarbazol-3-yl) ethyl] carbazol-2 (3H) -one (21 ) .We have reported that the indol-3-ylbutyric acid (1) reacts with trifluoroacetic anhydride (TFAA) to form the spiroketone (6). Attempts to repeat this reaction under the conditions described in ref. 1 with a fresh sample of the acid (1) did not yield (6); the only crystalline material isolated was the ketone (5). The i.r. spectrum of the compound contained a band at 1 650 cm-' (CO),* and the n.m.r. spectrum contained signals at 6 2.3 (CMe) and 3.65 (NMe), and showed the presence of only three ' aromatic ' protons. Reduction of the ketone (5) yielded the corresponding alcohol (7). When the acid (1) was heated for a longer time with TFAA the Cmethyl group of (5) was not attacked, the enoltrifluoroacetate (8) being isolated. However, heating the acid (1) with TFAA in benzene solution in the presence of sodium carbonate gave the known compound (6). These results suggest that (1) can cyclise in two ways to form either (2) or (4), and that a stronger base is required to convert (2) into (3) than is needed to create the aromatic structure present in (5). We have already commented on the reactions of 3-carboxy-1-methylindol-2ylacetic acid with acetic anhydride in the presence and absence of base.We have also examined the reaction of compound (10; R = OH), the lower homologue of (l), with TFAA. Neidlein had treated the acid chloride (10; R = C1) with aluminium chloride in benzene in an attempt to make the tricyclic ketone (12), but obtained the ketone (10; R = Ph), although cyclisations of b-indol-3-ylpropionic acids to form derivatives of benz[cd]indole have been accompli~hed.~ The acid (10; R = OH) was prepared by the known4*5u route from bpropiolactone and 1,2-dimethylindole. Since the reaction of Meldrum's acid with indole and aldehydes has been used to prepare b-indol-3-ylpropionic acids, we examined the reaction between 1,2-dimethylindole, formaldehyde, and Meldrum's acid in the presence of DL-proline, compound (9) being obtained. This was then boiled with ethanol-pyridine in the presence of copper powder and the crude ester (10; R = OEt) hydrolysed to the acid (10; R = OH). Under different reaction conditions 1,2-dimethylindole reacted with Meldrum's acid and formaldehyde to give the bis-condensation product (11). The n.m.r. spectrum of Meldrum's acid contains a signal at 6 1.76 from the CMe2 group; ' in the n.m.r. spectrum of the dioxane (9) these two methyl groups are non-equivalent,' having 6 1.60 and 1.75, but the signal from the protons of the CMe, group in compound (11) appears as a sharp singlet at 6 0.5 (1.26 p.p.m. ...
